As far as I understand, SSAA option was there from day-1, but broken, and was fixed sometime later.
Nowhere do I see the mention that it was removed entierly.

BUT.

I do not have this option under settings? Only FXAA, TAA and their combination.

Even if it is being set through GeForce Experience, it is being reset to TAA in-game.

What happened? Does anyone still have this option? Was it quietly removed because too many people don't know what they're doing?

Weird, I can't post an answer for my own question.

Anyway SSAA was confirmed to be removed in 1.3 update.

My screenshots look fine with AA applied

I think I had it set to TAA ( Low ) at the time, so maybe it depends on the type of AA you have enabled. But it definitely looked much smoother in-game than on my test screenshot.

Well, TAA works by blending the frames (thus Temporal) and will look significantly worse in a still image, yes.

Ah, I don't know much about the technology behind it. But that doesn't leave many options then, since they only have TAA and FXAA, and the latter option isn't really great either. Would be nice if they could provide Supersampling or something similar for screenshots at least.